1. Field of the Invention
The present invention relates to a constant velocity joint which may be mainly used in association with an automobile shaft, and also to a method of making an outer race used in the constant velocity joint.
2. Description of the Prior Art
A constant velocity joint has been well known in the art which comprises an outer race having a spherical inner surface formed with track grooves, an inner race having a spherical outer surface formed with track grooves, a plurality of torque transmitting balls sandwiched accommodated in between the inner race and the outer race, and a cage for retaining the torque transmitting balls. The outer race has an open edge formed with an entry chamfer to provide an outwardly flaring surface so that at the time of inclination of one of the inner and outer races relative to the other, a shaft mounted with the inner race will not collide against the open edge of the outer edge.
In making the outer race for this type of the constant velocity joint, the use of the working process in which a milling or grinding technique is used, tends to take a relatively long time to make, renders it to be difficult to achieve an increase in preciseness and tends to reduce the yield.
For this reason, it has hitherto been suggested in which (1) an entry chamfer of the outer race is worked on by the use of a plastic working process and the track grooves are formed by a milling process, and (2) the track grooves and the spherical inner surfaces are worked on by the use of the plastic working process and the entry chamfer is finished by the use of a mechanical process.
However, in the case where the track grooves are formed by the use of the milling process as described under item (1) above, difficulty has been encountered in that the precision of the track grooves cannot easily be increased and, accordingly, a grinding process is necessary to be performed after the milling process, resulting in increase of the number of manufacturing steps and, also, reduction in yield.
Also, in the case where the entry chamfer is finished by the use of the mechanical process as described under item (2) above, difficulty has similarly been encountered in that precision of the entry chamfer cannot easily be increased, accompanied by increase of the number of manufacturing steps and, also, reduction in yield. Since the entry chamfer is an element operable to regulate the maximum angle of inclination of the constant velocity joint, the entry chamfer is required to have a high precision.